Yesterday was a big Semantic Web hacking day. I spent a lot of it hacking on Redland's Python interface. Redland's a great C-based toolkit for RDF processing, written by Dave Beckett.
My current project using Redland is noodling with rdfweb.org-based projects, like "friend-of-o-friend." Currently I have a Python program that can figure out where pictures of people I know are. Lots of fun.